OLED display technology has the benefit of a wide operating temperature range, low power consumption, wide viewing angle, high contrast and fast response time making it the best choice for high-resolution displays. While the demand for OLED displays continues to increase, the technology still remains expensive to produce and lacks in overall resolution and performance quality.
Traditional OLED displays include a stack of thin layers formed on a substrate. A light-emitting layer of a luminescent organic solid, as well as adjacent semiconductor layers, is sandwiched between a cathode and an anode. The light-emitting layer may be selected from any of a multitude of fluorescent and phosphorescent organic solids. Any of the layers, and particularly the light-emitting layer, also referred to herein as the emissive layer or the organic emissive layer, may consist of multiple sublayers. In an active-matrix organic light-emitting diode the cathode may include an electrode having low work function, and the anode may include an electrode having high work function. Either anode or cathode may be transparent depending on whether a top or bottom emitting architecture is used.
In a conventional OLED device, when an electric current is applied across the device negatively charged electrons move into the organic material(s) from the cathode. Positive charges, typically referred to as holes, move into the organic material(s) from the anode. The positive and negative charges meet in the center layers (i.e., the semiconducting organic material), combine, and produce photons. The wavelength, and consequently the color, of the photons depends on the electronic properties of the organic material in which the photons are generated. Pixel drivers can be configured as either current sources or voltage sources to control the amount of light generated by the OLEDs in an AMOLED display.
The color of light emitted from the organic light-emitting device can be controlled by the selection of the organic material. Generating red, green and blue light simultaneously may produce white light. Other individual colors, different than red, green and blue, can be also used to produce in combination a white spectrum. The precise color of light emitted by a particular structure can be controlled both by selection of the organic material, as well as by selection of dopants in the organic emissive layers. Alternatively, filters of red, green or blue, or other colors, may be added on top of a white light-emitting pixel. In other examples, white light emitting OLED pixels may be used in monochromatic displays.
High-resolution active matrix displays may include millions of pixels and sub-pixels that are individually addressed by the drive electronics. Each sub-pixel can have several semiconductor transistors and other IC components. Each OLED may correspond to a pixel or a sub-pixel. Generally, however, an OLED display consists of many OLED pixels, and each OLED pixel may have three sub-pixels associated with it, in which each sub-pixel may include red, green and blue color OLEDs or may emit white light, which may be filtered to either red, green or blue. In order to obtain higher pixel density, the arrangement of sub-pixels must be more compact, thereby increasing the manufacturing burden and expense.
Traditionally, full-color OLED display panels include sub-pixel regions generally arranged in stripe form, mosaic form, or delta form. FIG. 1A depicts a conventional stripe OLED array as used in a variety of OLED display products. In particular, FIG. 1A illustrates a pixel device 100 in matrix form, which is composed of red, green, and blue sub-pixel regions 102, 104, 106. The sub-pixel regions 102, 104, and 106 are arranged in rows on a substrate. The pixel group comprised of sub-pixel regions 102, 104, and 106 is repeated identically along the rows and columns. While this is the most simplified arrangement for manufacturing and circuit design purposes, it provides the poorest color mixing effect.
FIG. 1B depicts a conventional mosaic OLED array 110, in which the pixel group formed from red, green, and blue sub-pixel regions 102, 104, and 106 is repeated identically along the rows and in which pixel groups between rows are separated by the width of one sub-pixel region. Using this sub-pixel arrangement, the color mixing effect is improved. However, the circuit design and driving method remain complicated.
FIG. 1C depicts a conventional delta OLED array 120, in which the pixel group formed from red, green, and blue sub-pixel regions is repeated identically along the rows and in which pixel groups between rows are separated by the width of 1.5 sub-pixel regions. Using this sub-pixel arrangement, the color mixing effect is still further improved. However, the circuit design and manufacturing process remain complicated.
Recent improvements to sub-pixel arrangements include PenTile® matrix which is a family of patented sub-pixel schemes specifically designed to operate with proprietary algorithms for sub-pixel rendering embedded in the driver, allowing for easy compatibility with RGB stripe panels. More particularly, PenTile® red, green, blue, green (RGBG) layout has been used in active-matrix organic light-emitting diode (AMOLED) displays whereby green pixels are interleaved with alternating red and blue pixels. FIG. 1D depicts a conventional PenTile® matrix, a registered trademark owned by Samsung, which provides good display performance with a reduction in pixel element count.
Regardless of the arrangement of sub-pixels used to achieve the full color display, the resolution is determined by the manufacturing process of the sub-pixel regions. A shadow mask, also referred to as a metal mask, alignment method is traditionally used to form the individual RGB color sub-pixels within a full-color OLED display, when the color sub-pixels are arranged in side-by-side format. As such, the resolution of the OLED display panel is determined based upon the opening dimensions of the mask and fine etching capabilities.
As can now be appreciated, there exists a need to provide a full color OLED display panel, in which each of the sub-pixels groups are designed in a specific arrangement and can cure some of the deficiencies in the prior art.
It is a primary object of the present invention to provide an OLED display, which utilizes a new OLED architecture with an efficient pixel arrangement manufactured using a shadow mask. The resulting OLED display is a small area display, which measures approximately 1 to 3 inches per side and is ideal for, amongst other things, high-resolution displays in demand for virtual reality headsets.